To distribute multicast packets, a multicast tree has heretofore been constructed by using a multicast routing protocol, e.g., PIM-SM (Protocol Independent Multicast-Sparse Mode), PIM-DM (Protocol Independent Multicast-Dense Mode), or DVMRP (Distance Vector Multicast Routing Protocol), for constructing a path with the minimum hop number to reduce a communication delay, and the resulting multicast tree is utilized for packet distribution (see, Japanese National Patent Publication No. 2004-531143).
Japanese National Patent Publication No. 2004-531143 discloses a virtual multicast network method and system in which packet distribution is performed based on a multicast routing protocol, e.g., PIM-SM, PIM-DM, or DVMRP, by using virtual multicast routers in a network that does not support multicast distribution.
However, if the multicast routing protocol, e.g., PIM-SM, PIM-DM, or DVMRP, is used in a mesh virtual network, packets are transmitted from the distribution source router to all the routers, and therefore a large load is applied to the distribution source router. Furthermore, the required bandwidth, delay amount, etc. differ between multicast groups (packet distribution destinations), which are constructed according to application software (hereinafter referred to as application).